1. CEPC partial double ring scheme and crab-waist parameters
Dou Wang, Jie Gao, Feng Su, Ming Xiao, Yuan Zhang, Jiyuan Zhai, Yiwei Wang, Bai Sha, Huiping Geng, Tianjian Bian, Xiaohao Cui, Yuanyuan Guo
CEPC AP meeting,

2. Primary parameter for CEPC double ring （wangdou20160325）
Pre-CDR
H-high lumi.
H-low power W Z
Number of IPs 2
Energy (GeV)
120 80
45.5
Circumference (km) 54
SR loss/turn (GeV)
3.1
2.96
0.59
0.062
Half crossing angle (mrad) 15
Piwinski angle
2.5
2.6 5
8.5
7.6
Ne/bunch (1011)
3.79
2.85
2.67
0.74
0.46
Bunch number 50 67 44
400
1100
Beam current (mA)
16.6
16.9
10.5
26.2
45.4
SR power /beam (MW)
51.7
31.2
15.6
2.8
Bending radius (km)
6.1
6.2
Momentum compaction (10-5)
3.4
2.2
2.4
3.5
IP x/y (m)
0.8/0.0012
0.25/
0.268 /
0.1/0.001
0.08/0.001
Emittance x/y (nm)
6.12/0.018
2.45/0.0074
2.06 /0.0062
1.02/0.003
0.62/0.002
0.62/0.0028
Transverse IP (um)
69.97/0.15
24.8/0.1
23.5/0.088
10.1/0.056
7/0.046
7.9/0.053
x/IP
0.118
0.03
0.032
0.008
0.005
0.006
y/IP
0.083
0.11
0.074
0.084 (Fl=3)
0.073 (Fl=2.6)
VRF (GV)
6.87
3.62
3.53
0.81
0.12
f RF (MHz)
650
Nature z (mm)
2.14
3.0
3.25
3.9
Total z (mm)
2.65
4.1
4.0
3.35
HOM power/cavity (kw)
3.6
1.3
0.99
Energy spread (%)
0.13
0.09
0.05
Energy acceptance (%)
Energy acceptance by RF (%) 6
2.1
1.7
1.1 n
0.23
0.47
0.3
0.27
0.24
Life time due to beamstrahlung_cal (minute) 47 36 32
F (hour glass)
0.68
0.82
0.92
0.95
Lmax/IP (1034cm-2s-1)
2.04
2.01
3.09
3.61

3. parameter for CEPC double ring-88km （wangdou20160318）
Pre-CDR
H-high lumi.
H-low power
Number of IPs 2
Energy (GeV)
120
Circumference (km) 54 88
SR loss/turn (GeV)
3.1
2.0
Half crossing angle (mrad) 15
Piwinski angle
2.6
Ne/bunch (1011)
3.79
1.75
1.53
Bunch number 50
257
176
Beam current (mA)
16.6
24.5
14.7
SR power /beam (MW)
51.7 30
Bending radius (km)
6.1
9.0
Momentum compaction (10-5)
3.4
1.9
1.5
IP x/y (m)
0.8/0.0012
0.36/0.0011
Emittance x/y (nm)
6.12/0.018
1.63/0.005
1.15 /0.0035
Transverse IP (um)
69.97/0.15
24.4/0.074
20.5/0.062
x/IP
0.118
0.04
0.033
y/IP
0.083
0.091
VRF (GV)
6.87
2.57
f RF (MHz)
650
Nature z (mm)
2.14
2.7
2.94
Total z (mm)
2.65
3.25
3.53
HOM power/cavity (kw)
3.6
2.2
1.1
Energy spread (%)
0.13
0.1
Energy acceptance (%)
1.4
Energy acceptance by RF (%) 6 3
2.1 n
0.23
0.29
0.31
Life time due to beamstrahlung_cal (minute) 47 32 40
F (hour glass)
0.68
0.78
0.82
Lmax/IP (1034cm-2s-1)
2.04
4.18
2.63

4. parameter for CEPC double ring-100km （wangdou20160318）
Pre-CDR
H-high lumi.
H-low power
Number of IPs 2
Energy (GeV)
120
Circumference (km) 54
100
SR loss/turn (GeV)
3.1
1.7
Half crossing angle (mrad) 15
Piwinski angle
2.0
2.83
Ne/bunch (1011)
3.79
1.43
1.22
Bunch number 50
436
307
Beam current (mA)
16.6 30 18
SR power /beam (MW)
51.7
Bending radius (km)
6.1 11
Momentum compaction (10-5)
3.4
1.8
1.4
IP x/y (m)
0.8/0.0012
0.297/0.0011
0.3/0.0011
Emittance x/y (nm)
6.12/0.018
1.63/0.0049
1.03/0.003
Transverse IP (um)
69.97/0.15
22/0.074
17.6/0.59
x/IP
0.118
0.033
0.025
y/IP
0.083
VRF (GV)
6.87
2.25
f RF (MHz)
650
Nature z (mm)
2.14
2.45
2.77
Total z (mm)
2.65
2.94
3.33
HOM power/cavity (kw)
3.6
2.3
1.1
Energy spread (%)
0.13
0.1
Energy acceptance (%)
1.46
Energy acceptance by RF (%) 6
3.5
2.2 n
0.23
0.27
0.28
Life time due to beamstrahlung_cal (minute) 47 40 49
F (hour glass)
0.68
0.8
0.85
Lmax/IP (1034cm-2s-1)
2.04
4.75
3.01

5. Luminosity vs circumference (Higgs)

6. y vs circumference (Higgs)

7. Bunch number vs circumference (Higgs)

8. Bunch charge vs circumference (Higgs)

9. Energy acceptance vs circumference (Higgs)

10. Bunch length vs circumference (Higgs)

11. SR loss vs circumference (Higgs)

12. Double ring FFS design with crab sextupoles
Betax=0.25m
Betay= m
K2hs=23.3 m-3
K2vs=-32.8 m-3
Crab sextupole
Critical energy: Ec=190 keV
Dipole strength: B=0.019 T IP
As Oide said, the second FFS sextupoles of the CCS-Y section can work as the crab sextupoles, if their strengths and phases to the IP are properly chosen.

13. Final doublet IP L*=1.5m L(QD0)=1.56m, G(QD0)=-200T/m
L(QF1)=1.53m, G(QF1)=98T/m
L0=0.85m

14. Crab sextupole strength
x=2, y=2.5
The crab sextupole should be placed on both sides of the IP in phase with the IP in the horizontal plane and at π/2 in the vertical one.
13% strength of main sextupoles

15. Thanks！